Project Summary: Accumulating evidence suggests that mRNA translation is altered in various neurological disorders. However, it remains largely unknown whether and how mRNA dysregulation contributes to disease onset. Microcephaly is a condition that arises in neurodevelopment characterized by smaller head size in infants that affects 6 in 10,000 children in the United States. Using a model of intracerebral inoculation of mouse embryonic brain, it has been established that intracerebral infection of the Zika virus during brain development can cause Microcephaly. The purpose of this proposal is to investigate if Zika virus (ZIKV) infection induces microcephaly through dysregulation of mRNA translation. ZIKV infection results in reduced cell proliferation, cell cycle arrest, and an increased apoptosis of Neural Progenitor Cells (NPCs), the cells considered to be most vulnerable in microcephaly. Recent work has reported that cells infected with the Zika Virus or other flavivirus family member Dengue Virus exhibit a decrease in mRNA translation of the host cell mRNA. Previously published work has also shown that knockout of the RNA-binding protein Lin28a leads to reduced NPC self-renewal and microcephaly in mice. Using mouse genetic tools, this study described that Lin28 can promote NPC proliferative cell behaviors, and that it may do so through modulating mRNA translation. Preliminary evidence has further suggested that reduced mRNA translation in NPCs is sufficient to cause microcephaly. These studies have collectively suggested that mRNA translation may be vulnerable in NPCs in Microcephaly, and identified that Lin28a gain- and loss-of-function mouse models are valuable genetic tools to manipulate mRNA translation specifically in NPCs. These major observations have led to the following hypothesis: The Zika virus causes Microcephaly through dysregulating global and gene specific host mRNA translation in neural progenitor cells. To address the hypothesis stated above, the following Aims will be performed: 1) Test to what extent mRNA translation dysfunction contributes to Zika virus-induced Microcephaly. To determine if increasing mRNA translation in NPCs can rescue ZIKV-induced microcephaly, the Lin28a overexpression mouse model will be combined with embryonic inoculation of ZIKV. This will help determine the impact or contribution that decreased host cell mRNA translation has in causing ZIKV-induced Microcephaly. 2) Identify what genes are differentially regulated in NPCs at the mRNA translation level in ZIKV-induced Microcephaly. To study mRNA translation specifically in NPCs in vivo, a novel mouse model will be used in which HA-tagged ribosomal protein Rpl22 will be expressed in a Cre-dependent manner and the resulting pull- down sample will be taken for RNA-seq. This will illuminate trends in mRNA dysregulation and provide the field with potential therapeutic targets in the context of ZIKV-induced microcephaly.!